Twist-drill.



J. WiNG & B. OREILLY. TWIST DRILL. APPLICATION FILED FEB. 9, 1909.

\ //v v5 70 P5 w/ TWESSES UNITED STATES PATENT OFFICE.

JAMES WING AND BERNARD OREILLY, OF SHEFFIELD, ENGLAND.

TWIST-DRILL.

T 0 all whom it may concern:

Be it known that we, JAMES WING and BERNARD OREILLY, subjects of theKing of Great Britain and Ireland, residing at St. Marys lVorks,Penistone Road, Sheffield, county of York, England, have inventedcertain new and useful Improvements in Twist- Drills, (for which we haveapplied for Letters Patent in Great Britain, No. 161 13, dated July 30,1908,) of which the following is a specification, reference being had tothe accompanying drawing.

This invention relates more particularly to drills which are constructedby twisting a flat (or approximately flat) bar of steel to the requiredhelical shape and to a separable and interchangeable shank which may becommon to a number of drills.

The chief object of the invention is economy, both in the manufacture,and also in the use of twist drills; the first being obtained bytwisting the helical portion of the drill from a fiat or preferablygrooved bar of steel, instead of cutting, grooving or milling the spiralgrooves from a solid bar, or from a partially formed spiral bar; thesecond object namely economy in use by our improved construction, isfound in the use of a separable interchangeable shank, by which in thecase of broken or damaged drills the loss of a valuable shank portion isavoided, instead of it becoming scrap as in the ordinary twist drills.

The sheet of drawings accompanying this specification illustrates ourinvention.

Figure 1, represents a length of flat steel with a groove on each side,shown in the end view. Fig. 2, the same bar with the grooved portiontwisted into helical configuration.

Fig. 3, the separable shank, and end view of same.

The shank portion A, of the bar, Fig. 1, is left in its flat shape, butis made slightly tapering upon its edges A to conform to the Morse orother standard taper, and we also prefer to give a slight taper to theflat sides of same to a prearranged standard gage. The part B, which isto be twisted may be fiat but as the result of experience Specificationof Letters latent.

Application filed February 9, 1909.

Patented Apr. 5, 1910.

Serial No. 476,920.

we prepare this part before twisting with a groove 0, down each of itsfiat sides. Such grooves are broad and shallow as shown in the end viewFig. 1, reaching from one edge of the bar (for example) to within athird of its width from the other edge, or thereabout, a-nd'becomingshallower toward the shank. These grooves may be produced by rolling,milling, or other preferred process, and when the bar is twisted by theapplication of force applied in any approved manner, the grooves producea cutting edge at the desired angle and leave the maximum of strengthatthe back to sustain the torsional strain occurring during drilling.

The detachable shank is shown in Fig. 3; it is of tapered configurationto conform to the standard tapers of the several sockets in use, and isprovided with a slightly tapered open side slot D, into which thetapering flat end of the drill will fit but leaving a vacant spacebetween the end of the drill and the bottom of the slot D.

When placed in the socket of a drilling machine spindle, the drill isheld perfectly true and secure.

We are aware that to produce the spiral part of drills by twisting thematerial to the desired form in contradistinction to cutting the groovesfrom the solid bar is not in itself novel, and we do not seek to claimsuch per 86.

Having now particularly described our said invention we declare thatwhat we claim, is

A twist drill comprising a flat bar having its lower portion twistedinto helical form and having its upper portion fiat and slightlytapering upon its flat sides and edges, and an interchangeable shankhaving an open sided tapering recess to receive said upper portion.

In witness whereof we have hereunto set our hands in presence of twowitnesses.

JAMES WING. BERNARD OREILLY. VVitnesses':

Ensor. D. DRURY, BERNARD E. DRURY.

